Catalytic dehydrogenation of hydrocarbons



July 19, 1960 D. s. ALEXANDER ETAL 2,945,900

CATALYTIC DEHYDROGENATION oF HYDRocARBoNs Filed Sept. 5, 1957 N... v. ig l NNNN QN i ...IPL

that'is,

l hydrocarbons. 1

i .fCATALYTICDEHYDROGENATIGNOF HYDRCRBONSY Douglas Sadler tario, Canada,`assignors to Polymer Corporation Limited,` Sarnia, Ontario, Canada, a body corporate and 'nnedsept.:e19s1,ser. Nessuna y s climsf pri .2o ,Claims Vrcli 26o-669.12

This-inyentionlrelates td animproved process `for the catalytic dehydrogenation of hydrocarbons. It. relates particularly' to .improvements in the dehydrogenation of hydrocarbons'inthe presence of-calciu'm nickel `phosphate-type catalysts, `andmore particularly to improvements f in the vmethod offproducing olelinic hydrocarbons suchas butadiene-1,3 and styrene by the. dehydrogenation of lmoresaturated compounds. v

f e Vcatalytic.dehydrogenation of hydrocarbons in the Alexander and-*john Firkd, sanita, oli-V .l V. l v j throughthe catalystbed, while theregeneration period ority, applcationcanada Aug.rl,f1ol57 i y United Smeg ice to 'use fa,V cyclic process comprising alternately. electin'g' dehydrogenation of the hydrocarbon and removal of the carbonaceous deposit from the catalyst. The part of the cycle during which the hydrocarbon 'is' dehydrogenated is called the process period while the part in which the carbonaceous deposit is oxidized is called the regener-v ation period. In the case of a calcium nickel phosphate'- type catalysttheprocess period is normally eifected at temperatures'be'tween about 550 C. and about 6509,C. by passingla mixture of the hydrocarbon and steam `after 'process' periods of from about 30 to about 90 Vminutes. The cyclic operation of dehydrogenating the hypresence. of calcium` nickelv phosphate-type catalysts is disclosed generally. in United stares' Patent No. 2,442,320 issued,May:`2r5.l948.toEdganCQBritton etal. `Such dehydrogenationreactions are neverv completely selective; sifn'possible to produce a pure productbecause of side reactions which resultinl ,ayariefty'pf by-products. (Conversion is hereby'jfdened as .the percentage of the hydrocarbons passing [over the catalystwhich is converted.

drocarbon and'regenerating the catalyst is believed, to be harmful to the lifeY of dehydrogenation catalysts. Normally, catalyst life is about six months and because of the large amounts of catalyst used, it is desirable to extend the life of such catalyst as -much as possible. In other words, it is desirablerto reduceV the rate of carbon deposition on the catalyst during the process period since this decreases theA number of cyclicoperations required in any given period of time and not only tends to extend the'catalyst life but also permits increased production perv lllliltillfliv Y Y Accordingly, it is an 'object of the present invention todisclose an improvedV processffor the-"catalytic de- Y hydrogenation of hydrocarbons wherein theY percentage Percent.selectivity'` Idefined asthe number of Vmoles of A ded by the numb'e'rfof moles 'i of hy- `selectivity.)f,Becaus e .ofi this tendency ,to produce .byproducts, 'SucliIdehydrOge'natOn reactions arestopped shortof completion, the actual Vcc'mt'fersion depending upon thefeconomic considerations of the particulargprocess.

In. fact, jthe conversion of ,hydrocarbon in aj single contact `dehydrofgenation operation is frequently, less than 'T50 percent.' 'Furthermore fthe .product stream often con- `"tains"onlyabout 1,5-30'pereentby weightof the. desired hydrocarbon compound; the; proportion depending upon thelselectivity of the reaction," AHence, in ,order to obtain substantially pure product and also"` not. towasrt'ethe: `u n- Y converted' hydrocarbon, it 'ish necessaryk .to j separate vthe desired compound from thevreation product stream .and to recycle "the remainder of the stream and recontactit -with the .dehydrogenation catalyst. Y e Y Extraction ofthe desired compound from the reactor product stream is normally carried out at'a'low temperature andthe unconverted hydrocarbons therefor require reheating before being,recycled.'V For example, it is common vpractice toextract butadiene-1,3 from a dehydrogenated n-butylene stream 'by contacting14 the stream with an ammoniacal cuprous acetate solvent at temperatures ranging frmabout 16 C. to about 0 C. It is readily appreciated that itis desirable.V to eiect as` high a` conversion as possiblefor '-eachcontacting operation with the dehydrogenation catalyst, and as complete a separaconversion is increased signiicantly.

It is a further object to'increase the life 'of a calcium v nickel phosphate dehydrogenatin catalyst bydecrcasing the rate of deposition of carbon thereon. e

It is la further object of the invention to vincrease the y catalyst life by operating at lower feed temperatures.

These' and other lobjects of the-present invention are i achieved in the-process of dehydrogenating a hyldrc'scar.-

` hydrocarbon.

, oxygen.

bon selected Vfromtheclass consisting of mono-oletins and alkylated aromatics which comprises passing said hydrocarbon together with steam at a..vdehydr`ogenation temperature overa dehydrogenation catalyst, the active ingredient of which is calcium.- nickel phosphate by the improvement which comprises carryingV out said dehydrogenation in thepresence of from about 5 to.about 40 parts of uncombined oxygen, based Von the volume of said The present invention is based on the discovery* that Athe presence of a substantial amount of oxygen inthe reactor during dehydrogenation in the presence of calcium nickel phosphate-type catalystv results in a substantial-increase in yield. There'is also a surprising decrease inthe rate of deposition of carbonaceous material on the catalyst so that they activity of the catalystdecreases more slowly during the processperiod than is the casein the absence of YIn the practice ofthe invention, the catalyst bed is v heatedV to the` desired reaction temperature before Vthe tion as possible of the desiredcomponents from` the recausing af gradualfreduction -in its activity.f Therefore,

to maintain the' activity of the catalyst itis necessary to remove the carbonaceous deposit periodically. `It 1s .general practice in such catalytic dehydrogenation operations,

admission of hydrocarbon,.preferablybygpassing therethrough steam superheatedto a suitably high temperature. However, it may' also be brought to the desired tempera ture" bythe application fofQexternalheat .to the reactor. The hydrocarbonand steam are ,usually heated .in separate furnaces andgjthen admixed before contact with the catalyst, the hydrocarbon to Vabout 450 C. to about 55,0*a

C. and the steam to abord-700 C. to Yabout 850 C."orV higher sothat a mixture of the two has the desired Vre action temperature of about 550 C. to about 6501 C. The heat may also be supplied by forming the steam and hydrocarbon mixture at'alower temperature and passing the mixture through a preheater to bring it to the reaction ijatented July i9, 1960 3 temperature or by externally heating the reactor containing the catalyst.

Oxygen may be introduced into the system in any satisfactory form so long as it is present in the'reactoi inv uneombinedform. Uncombined oxygen is herebydeiined as oxygen which is not combined with any other element'but exists as '0, O2 or O3. It may be'introduced as substantially pure oxygen or in atmospheric air, or itmay b'e introduced in a compound such as hydrogen peroxide, which liberates oxygen under the conditions prevailing in thedehydrogenation reactor. Other compounds Vwhich can be used satisfactorily include nitrogen dioxide,V sulphur'trioxide and organic pcroxides andhydroperoxides such as ben'zyl peroxide, cumene hydroperoxideV and, diisopropyl benzene hydroperoxide. Obviously, theoxygen cannot be introducedv in combinedform in a'compouud whiehyon decomposition, will form a'byfproductthat is'injurious to the dehydrogenation process.- For"example,perchloric acid cannot be used since its decompositiongresults in the production of chlorine and chlorine is known to be a poison for calcium nickel phosphate dehydrogenation catalysts. Those skilled in the art are readily able to select compounds 'which may be used'satisfactorily as oxygen sources. l

' The oxygen source may'be introduced into the reactor in various ways. It may be admixed with relatively cool hydrocarbon or`with'the steam, or it may be added diectlyto' the reactor. -However, it is important to add the oxygen in such a way' that is in dilute form before coming in co'nta'ct'with hydrocarbon at a high temperature. This procedure"reduces the danger of Vallocalized higl1 concentration of oxygen resulting in a partial burning'of Athe hydrocarbon. Foriexample, if hydrocarbon and steam are adrm'xed beforef'passag'e through a'preheater to bring theintorea'ction temperature, the oxygen source may be mixed satisfactorily with either thelhydrocarbon or the steam. It the hydrocarbon is heated to a high temperature, before admixture'with .the steam, it is necessary'to adm x the oxygen with the steam s'othat the oxygen is highly diluted before'contactin'g the hydrocarbon.

TheV concentrationof oxygenwhic'hit is desirable to have'in' thereactor lies gen erally"between about 5 -and 'about 40 volume percent and preferably from about 10 to about`30 volume percent vbased on theV hydrocarbon feed. Such concentration dependsV upon variousV conditions. In 'generaL-'the hydrocarbon conversionincreases Las' the concentration of oxygenincreases, with no appreciable drop inpzselectivity, up to a maximum, after which the Vselectivity gradually decreases with a furtherincrease in oxygen concentration. The optimum concentration under any "given set of conditions ca'n be readily determined by those skilled in the art. It dependson the dehydrogenation temperature land the particular catalyst'being used. Pur therniore, such catalysts generally decrease in activity with-'continued use so that operating conditions must be varied'slightly as the catalyst ages, for example by use of `a higher reaction temperature.

The quantity. of steam used may vary widely and is' generally between about 10 and about 50 volumes per volume of'the hydrocarbon vapor'being dehydrogenated. The dehydrogenation reaction is usually carried'out at about atmospheric pressure, for convenience, but higher or lowerv pressuresrmay be' used if desired. VFor best results,'the hydrocarbonsteamoxygen mixture should be contacted withthe c atalystV for only a short period of tithe, although a short Contact timeisnot essential for success. 'It is usually desirable to utilize `a contact time between Aabout 0.25 and 1 second, although times outside this range can berused without departing from the s'c'opefof theinvention The optimum 'contact time varies wit-h'the Vparticular hydrocarbon being dehydrogenated, the reaction temperature and the hydrocarbon/ steam ratio. To prevent the catalyst from becoming "inactive due to the accumulation of the carbonaceous deposit-it is re- .generated periodically. In effecting the regeneratiomthe flow-of hydrocarbon and oxygen is Vrststopped and suitable hydrocarbons are those which are disclosed and oxygen is introduced together with the steam at a controlled rate in order to remove the carbonaceous deposit without causing a sudden rise in the temperature of the catalyst bed. When the regeneration is completed, the flow of regenerating oxygen is stopped, the reactor ushed with steam and the ilow of hydrocarbon and oxygen resumcd. Obviously, the regenerating 'oxygen may be supplied by air or by the same oxygen source as that used during the process period.

The hydrocarbons which may be dehydrogenatedaccording to the present invention are any of those which may -be catalytically dehydrogenated in the presence-of a calcium nickel phosphate-type catalyst. Examples of claimedv inV U.S. Patent No.' 2,442,320 issued May 25, l948to Edgar C. Britton et al. Such hydrocarbons include oleiins having in the molecule at least four carbon atoms in the carbon chain containing the' olelinic. linkage; examples include butylene, pentene 'and'hexene The invention is particularly useful in dehydrogenating olelins havingfrom four to six carbonatoms in the'molecule and only four carbon atoms in the' unsaturated to form the corresponding conjugateddioletinsgeg. n-butylene may be dehydrogenated-to'produce butadiene-l,3 and isopentene may be dehydrogenated to produceiso-` prene. The Vinventionis -alsfo usefulin dehydrogenating hydrocarbons which have a center ofvunsaturation other than an olelinc linkage (for example, 'for dehydrogenating hydrocarbonsY containing a benzene ring).- Fortinstance,'alkyl aromatic hydrocarbons'havin'g at least two carbon atomsin the alkyl group can 'be advantageously dehydrogenatedto the correspondingolein by' the'A process of the present invention'. Thus, styrenegcan'be.pro`duped by the dehydrogenationA of ethylbenzene. v

The reason for increased conversion -of oleiins and aromatic compounds when dehydrogenation Vover lealcium'nickelV phosphate catalysts was carried out 'nlthe presence of oxygen is not completely understood butso far as the `inventors have been able to determine,y the eiiect is produced only with dehydrogenation catalysts` in kwhich the `active Vingredient is vcalciumfnickel phosphate'. An `attempt was madefto increase the conversion 'of butylene's'to butadiene-'1,3 aridof ethylbenze'ne to styrene byconducting the dehydrogenation in the. presence 'of 'added loxygen using a conventional `iro'n'oxide dehydrogenation catalyst such as that disclosed in UnitedStates Patent No.,2,426,829 issued to K. K. Kearbylon Septem.- ber 2, "1947. ItWas'found that the:activity'ofithecatalyst 'was significantly reduced in comparison with operations Y,in the absence of oxygen.` Similar unsatisfactory results were obtained Yin dehydrogenating butylene over-a zinc oxide catalyst 4and butane over a conventionalchro'mealumina catalyst. One method of practisingthe present inventionon a laboratory scaleV is illustrated -diagrammatically inf'the accompanying ligure. vReference numeral 10 designates aglass reactor tube carryingY catalyst pellets 11 and located in the electric furnace'lZ which is heated by electrical heating elements 13., The temperature'insidethe tubeis measured by thermocouple 14. Container 15 is a Water reservoirwith-a constantbend connected by line 16 carrying 'stop-cock' A`17 and -passing A through -stopper '18 into a Vgraduated cylinder 19. Also passing through .,rounded "by, heating Yjacket 30, which Vcarries?electrical.

heatingelementl 31. Tube 32fconnects the steam-lgenerator -1'26 to .the-1- reactor tubeflO by means: ofcouplingf33. Y'fuerendi-nf'theireactor:tuberfremote from -thesteam Ygeneratdr isvfconnected' to the lowerjend'of awater-cooled condenser 34 vand to condensate receiver' 35. YTheupper end of the condenser 34 is connected through tube 36V to the upper endV of a product receiver 37 ,equipped with stop-cocks'38 andV 39. The lower endjof receiver 37 is in turn connected to a levelling bulb 40 by: meansjof tube41.. Y.

In carrying outf'catalytic dehydrogenation reactions using the hereinabove described apparatus, the following procedure may be adopted: First, the graduated cylinder 19 is completely lled .with Water. 'I'.hen with stop-cocks 17 and Z5 closed and with stop-cocks 21 and 2.3 open, the hydrocarbon to be dehydrogenated and oxygen are introduced through line 22 displacing Water through line to the drain until the desired volume Aof hydrocarbonoxygen mixture is present in cylinder 19. Nextpstopcocks 21, 23 and 28 are closed and stop-cock 25 opened. Stop-cock 17 is then opened and water'allowed to flow from reservoir 1S through line '16 and into cylinder 19 at a controlled rate. The gas in cylinder 19 is thus forced through line 24 and into steam generator 26 where it bubbles through heated Water and, in admixture-.with steam, passed through lineS-Z and thence .to reactor .tube 10. The reactor product passesto the `water-cooled condenser 34. Steam condenses to waterv and is collected in receiver 35. The uncondensed vapours pass from the upper-end of the condenser through line 36 and into product receiver 37. As the product enters receiver37 it dsplaces Watertherefrom into a levelling ,bulbv 40 lwhose height is `continuously adjusted to vretain-tain the pressure in the reactor'tube as constant asV possible. When receiver 37 is filled with product, stop-cocks 38 and Va*chromela1limel thermo'couple-plac'ed near the gas exitend ofz the catalyst bed and Vabout 6 inches inside the furnace.A The steam Wasicondensed and the hydrocarbon collected in a receiver. f ,The hydrocarbonproduct was analyzed for butadiene-1,3 by a gas chromatography, by mass spectrometry, and;by"infrafred-techniques The catalyst was regenerated inthe conventional manner by passing avmixture of air and steam over it at'the dehy= y drogenation temperature. This, dehydrogenationqegeneration' cycle was repeated a number of 'timesand theresults are shown in Table I. l v

Y The" operations .of repeated except the butene-l was"rep1ac'ed"'by.l800 mls; of a mixture of butene-'l andlox'ygen in which oxygen made up'20 per-V cent by volume. The results are shown in Table II.

139'are closed. Thereceiver is then disconnectedgand its y contents analyzed by conventional methods.

'Ilhe temperature of the reactor tube carrying the catl alyst in pellet form is controlled at the desired level by regulating the voltage of the electric supply to elements 13. The hydrocarbon enters the steam generator at room temperature and leaves in admixture withV steam at a temperature'of about 100 C. The ratio of steam to hydrocarbon leaving the generator Vis regulated by the electrical input to theh/eating element 31 and'is readily determined by measuring the rate of accumulation of water in receiver 35 which is conveniently a graduated cylinder.

Regeneration of the catalyst is effected by closing stopcockZS, opening stop-cock 28, and forcing controlled amounts of an oxygen-containing gas such as air-through line 27 into line 24 and` through steam generator y26 where it is admixed with stea-m. Ater a .suitable-regeneration period the catalyst ,is readyor a resumptionof dehydrogenation operation.

The following examples will further-illustrate thepraci tice and advantages ofthe present invention, using, in all but ExampleGI, the apparatus hereinabove described. 'I'rhe catalyst used in all of the examples was a commercial calcium nickel phosphate-chromium oxide cata lyst of the type described in United States Patent No. `2,442,320 issued May 25, 1948 Vand preparedin accordance with United States Patent No. 2,542,813 issued February 20, 1951 to S. B. Heath. A typical chemical analysis of such catalyst in weight percent is: nickel, 5.0; calcium, 370.3; phosphate radical, 53.2; chromic oxide, 2.9; graphite, 2.4. g t -r EXAMPLE I y a 1800 mls. of research grade butene-l -vveremixed` with steam in the ratio of about ,1 :'40 partsbyvolume'by passing the butene through boiling water.` The irlixture was passed at the rate of 30 mls. Yper 4minute of butene-l measuredat room temperature and atmospheric pressure Aover l0 grams of catalyst containedin'a'quartztube. "Ihecontct'time ofthe hydrocarbon with the catalyst was about' 0.25 second; Y The tube and contents ,were

Vmaintained at 650 C., overfa length off24 inches, in an electric furnace. The temperature was measured by Table `11.-.i12ehydrogerila"tio-n btene-I in the Y* of. 20 lvolume percent oxygen SampleNo. VSteam/HC Percent Percent ield ofg: (Volumes) Conversion selectivity lB utadi-` f enefl On comparing -theseresults with those of .Table I lit isV seen thatthepresence of .20' percentfr oxygen results in` a substantial increase in the'conversion offbutene-llto butadiene-1,3. v

EXAMPLE III" The elfect ofoxygen concentration on the ldehydrogenation of buten'e-l at575 C. 'wa s tested `'by dehydrogenat ingVbutene-l 'accqr'dingto-Exampl'II except fth'at the proportion ofoxygen in. the 4Vfe'edfwasvaried; Theresults are shown 'Ilable III.

Taslilre IIL-Effect lof 02 concerttration on dehydrogenatwn of butene-I at 575 C.

Oxygen t Percent added Percent Percent Yield of Percent Sample No (Vol. per- Conv. Select. Buta- Increase cent of diene-1,3 in Yield butene-l) 1*, 0 22.5 97.7 22.0 5 27.9 95. 6V 26.5 20.4 l0 31.2 94.4, 29.5 33.8 15 37. 6 87.6 33.0 50. 0 2o 30.5 f 89.3 .27.2 23.6 30 v30.0 80.4 VV25.9 M11-:.5

*Sample 1 the average of six results, Samples 2-6 are* each the average of2results.VV f v i The 'effect et 'oxygen concentration on' the V'deliydro-V genation oftbutene-l at 610 C. was tested by dehydro genating butene-'l according to Example II except that theproportion bf oxygen'intheffeed wasvaried. The results are showni'nTable 1V. Y

Table IVF-Effect of 02 concentration on dehydrogenatz'on of butene-I at 610 C.

Sample 1 is the average of six results, Samples 2-6 are each the average of two results.

EXAMPLE V The eiect of oxygen concentration on -the dehydrogenation of butene-l at- 660 C. was tested by 4dehydrogenating butene-l according to ExampleIIexcept that the proportion of oxygen in the feed was'varie'd. The results are shown in Table V.

Table V.-E1ectof O-aconcentraton'on dehydrogenation of Vb'utene-I Vat 660`C.

`Oxygen n Percent Y l added Percent Percent Yield of Percent Sample No. (Vol. per- Conv. Select. Buta- Increase cent of diene in Yield EXAMPLE VI Y Theetfect of air on the dehydrogenating of .butene-l at 650? rCwastestefd by dehydrogenating butenefl alone as in VExample I and mixedwith oxygenasin Example II except that the oxygenwassupplied-by 25, 50'-and-70 volume percent of air. The results fare `Yshown in Table VI and are similar to those obtained in Example II using corresponding amountsV of oxygen..

Table VI.-E,ect of air on the -catalytc `dehydrogenaton of butene-I at 650 C.

Air

Percent 1 Percent. Yield of` Sample No.

. Percent Conv.

Increase` in Yield .5.55.5 zen-eme ExAMPLEyn v Y 1800 mls. of butene-l were mixed with steam inv-the Percent;

8 ratio of about 1:40 parts by volume as in Example I and hydrogen peroxide rwas added to the mixture from a bui-'ette at such a'rate as to produce, on decomposition, 20% byvolume of 'oxygen on the butene-l. The 'mixtureiwas then dehydrogenated as in Example I. The results 'are shown in Table VII.

Table VIL-Dehydrogenaton of butene-J al'650 C. n

' the presence of H202 Steam/HC Percent Percent Percent Sample No. (Volume) Con- Selectivity Yield version Butadteue vEXAMPLE VIII Atest was carried out to show the rate of decreaseof activity 'of a calcium nickel.' phosphate-chromium oxide catalyst with'the1 length of the process period. Butene-l was'dehydrogenated as in Example I except that the process"perio'd"was'ontinued'for 141/3, hours without regenerating ythe catalyst. Thenthe test was repeated using a butene-l oxygen mixture as in Example II except that the process period wascontinued for 10% hours without regeneratingithecatalyst. Samples of the'product taken at intervals were analyzed and the results are shown in Table VIII.

Table 2VlII.-"Eect of pracess'period length on catalyst l i activity Y Y v' VrPure Butene-l Butene-i Containing 20% Og` ATime of Run ""(hrs.) Per- VPer- Per-v Time Per- Per- Percent cent cent of Run cent cent cent Conv. Select. Yield (hrs.) Oonv Select. Yield *Mt- 42.78 93. 6 40. 0 51. 9 92. 6 48. 0 V3 41.3 92. 5 38. 2 50. 2 91. 2 45. 8 51.6 92.0 47.5 6% 34.3. 94.2 32.4 41.7 92.6 38.6 87/a----. 32.6 94. 3 30.7 47. 5 91.5 43. 5 45 1444...-- 21.8 94.8 20.6 48.9 88.6 43.4

fThese results show that when oxygen is present during Ithe dehydrogenatiom the catalyst lactivity decreases much more'slowly-t-han in the'absencel of oxygen. It is seen vthatin conventional operation thepercent conversion decreasedlfrom'42-8'to 32.6 in 8%2 hours and to 21.8 in 141/3 hours, while the yield dropped from 40.0 to V30.7 and20.6, respectively. On the other hand, when the btene contained 20% oxygen the conversion only decreased from 51.9% to 48.9% and the yield only decreased from 48.0 to 43.4% in 10S/s hours. Therefore, it is possible to operate satisfactorily for long process periods when oxygen is present, thus reducing signicantly thehun-productive portion of conventional dehydrogenationY operations.

EXAMPLE IX To test the rate of carbon deposition on( the catalyst, butene-l and mixtures of butene-l with 15 and 20% oxygen were dehydrogenated as in Examples I and II. After a process period of one hourv the reactor wasl purged of v hydrocarbons with steam. Then air was passed through the reactor to oxidize deposited carbon. The eiuent carbon dioxide was removed in a calcium hydroxide solution scrubber and the amount of carbon ca1- culatedfrom the weight of the resulting precipitate. The results are shown in Table IX and indicate that the presence-of oxygen Vdur-ing the dehydrogenation reaction resultsin a surprising reduction in the amount of carbon deposited. on the catalyst.

The experiment of run 1 was The results are ing the addition of oxygen after a subthe presence of oxy'gen repeated inruns 2 and 3 except -that the temperature was z .i 600 C. and that further blank dehydrogenationsfwere j Carbon Deposited 5 eed by Stopp stantial number of cycles and dehydrogenating the hydrocarbon in the conventional manner.

shown -Table XII.

RUN #1 -REACTION TEMPERATURE 560 o.

Samples of the product were taken periodically and ana'-4 lyzedI for butadiene-1,3.

-p`er Gram of Butene-1 Passed Over Catalyst (Grains)` 2 10` 103 10 Table XII.-`Plot plant dehydrbgenqiion of butene-I in phatechromum` oxide catalyst during one hour ofVdehydrqgena'tio reactionv at 650- C. L

VPercent: A

Oxygen Concentration in Bterne-l, Feed Voli Table IX .-i-'Calrbon Y deposition Aon calcium 'm'ickl phosin the selected from the class consisting of mono-olefins and 65 alkylated aromatics which comprises passing said hydrol i Y presence of; oxygen Rate of Ethyl-l benzene addition Tdble XI.-Dehydr0genation of'V ethylbenzene Reaction EXAMPLE XII h 1 Volume ot ethylbenzene/volume oi catalyst/hour is the volume of ethylbenzene at N.T.P./volume of catalyst] Butene-l was dehydrogenated at 560 C. on a pilot plant scale over the same catalyst as used in the laboracarbon together with steam at a dehydrogenation temperature over a dehydrogenation catalyst, the active ingredient of which is calcium nickel phosphate, the improvement which comprises carrying out said dehydro genation in the presence. of between about 5 and about 40 percent uncombined oxygen, based on the volume of said hydrocarbon. 1011 achleved 1D he 2. In the process of dehydrogenating a mono-oleuic absence of oxygen. When this value had been established hydrocarbon containing at least four carbon .atoms in tory scale apparatus. Alternating process' and regeneration periods of one hour were used. The ratio ofY steam to hydrocarbon was 20/1 on a volume basis and the con- 70 tact time was 0.5 seconds. VAt the beginning of the run no oxygen was introduced with the hydrocarbon in order to establish a value for the convers oxygen was introduced in adxnixture with the steam. 75 the olenic chain which comprises passing said hydrocarbon together with steam `at .a dehydrogenation temperature'over ya dehydrogenation `catalyst, the active ingredienttofwhich is calciumnickel phosphate,"the:improvement which comprises carrying outsaid dehydrogenation inthe presence of' between aboutS and about 40 percent uncombined oxygen, Vbased on. the volume of said hydrocarbon. Y

3. In the process of dehydrogenating aYmonoi-olenic hydrocarbon containing from four to six carbon atoms in the-.olenic chain which comprises passing saidhydrocarbon together with Vsteam'ata dehydrogenation temperature over a dehydrogenation catalyst, the active ingredient of which is calcium nickel phosphate, the improvement which comprises carrying out said dehydrogenation in the presence of between about and about 40 percent uncombined oxygen, based on the volume of said hydrocarbon.

4. The process as claimed in claim 3 in which said mono-olenic hydrocarbon is normal butylene.r

5. In the process of dehydrogenating an alkylated aromatic hydrocarbon having at least two carbon atoms in the alkyl chain which comprises passing said hydrocarbon together-with steam at a dehydrogenation temperature over a dehydrogenation catalyst, .the active ingredient of which is calcium nickel phosphate, the improvement which comprises carrying out said dehydrogenation in the presence of between about 5 and about 40 percent uncombined oxygen, based on the volume of said hydrocarbon.

6. The process as claimed in claim 5 in which said alkylated aromatic hydrocarbon is an ethylbenzene.

7. In theV processof dehydrogenating a mono-olenic hydrocarbon having at least four carbon atoms in the oleiinic chain which comprises passing said mono-olefinic hydrocarbon together with steam and at a temperature between 550 C. and 650 C. over a dehydrogenation catalyst, the active ingredient of which is calcium nickel phosphate, the improvement which comprises effecting such dehydrogenation in the presence of between about 5 and about 40 percent uncombined oxygen, based on the volume o f said mono-oleflnic hydrocarbon.

8. Theprocess as claimed in claim 7vin which said mono-olenichydrocarbon contains'four carbon `atoms in the olenic chain.

9."The process as claimed in claim 7 in'whi'chsaid mono-olenic hydrocarbon is normal-butylene.

10. In the process of dehydrogenating normal butyleneV which comprises Vpassing lsaid normal butylene' together with steam and at a temperature of S50-650 C. over a dehydrogenation catalyst the active ingredient of which is calcium nickel phosphate, the improvementV which comprises effecting such dehydrogenation in the presence of between about 10'andl about 30 parts of uncombined oxygen, based on the volume of said normal butylene.

11. In the process of dehydrogenating ethylbenzene which comprises passing ethylbenzene togetherV with steam and at a temperature of S50-650 C. over a dehydrogenation catalyst, the active ingredient of-which is calcium nickel phosphate, the improvement Vwhich 1-2 comprises -efectingA such dehydrogenation inthe presence of'between about 10-and about 30 parts of uncombined oxygen, based on the volume of said ethylbenzene.

12. The process as claimed in claim 10 in which said oxygen is mixed in substantially pure form with said steam before entering the dehydrogenation reactor.

13. The process as claimed in claim 11 in which said oxygen is mixed in substantially pure form with said steam before entering the dehydrogenation reactor.

14. The process as claimed in claim 10 in which said oxygen is introduced by mixing air with saidv steam before said steam enters the dehydrogenation reactor.

15. The process as claimed in claim 11 in which said oxygen is introduced by ,mixing air with said steam' before said steam enters the 'dehydrogenation reactor.

, 16. In the process ofdehydrogenating a hydrocarbon selected from theclass consisting of mono-oleiusand alkylat'ed aromatics which comprises passing said hydrocarbon together with steam and at a temperature of S-650 C. over a dehydrogenation catalyst, the Aactive ingredient of which is calcium nickel phosphatechromium oxide, the improvement which comprises admixing betweenI about 5 and about 40 parts of uncombined oxygen, based on the volume of said hydrocarbon with said steam before it is introduced to the dehydrogenation reactor.

17. ,The process as claimed in claim 16 in which said mono-olefin is normal butylene.

18. The process as claimed in claim 16 in which said alkylated aromatic is ethylbenzene.

19. In the process of dehydrogenating normal butylene which comprises contacting said normal butylene, admixed with steam and at a temperature of S50-650 C. with a calcium nickel phosphate-chromium oxide'dehydrogenation catalyst, the step which comprises Vadmixing between aboutlO and about 30 parts of uncombined oxygen, based on the volume of said normal butylene, said steam before said steam is mixed with said normal butylene.

20. In the process of dehydrogenating ethylbenzene which comprises contacting Vsaid ethylbenzene, `admixed with steam and at a temperature of S50-650 C. with a calcium nickel phosphate-chromium oxide dehydrogenation catalyst, the step which comprises admixing between about 10 and about 30 parts of uncombined oxygen, based on the volume ofs'aid ethylbenzene with saidV steam before the steam is admixed .with said ethyli benzene.

*References Cited in the le of this patent UNITED STATES PATENTS 

1. IN THE PROCESS OF DEHYDROGENATING A HYDROCARBON SELECTED FROM THE CLASS CONSISTING OF MONO-OLEFINS AND ALKLATED AROMATICS WHICH CONPRISES PASSING SAID HYDROCARBON TOGETHER WITH STEAM AT A DEHYDROGENATION TEMPERATURE OVER A DEHYDROGENATION CATALYST, THE ACTIVE INGREDIENT OF WHICH IS CALCIUM NICKEL PHOSPHATE, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID DEHYDROGENATION IN THE PRESENCE OF BETWEEN ABOUT 5 AND ABOUT 40 PERCENT UNCOMBINED OXYGEN, BASED ON THE VOLUME OF SAID HYDROCARBON. 